DE2246972A1 - AUTOMATIC FREQUENCY CONTROL SWITCHING - Google Patents

Description

DR. BERG DIPL.-ING. STAPF

PATENT LAWYERS S MUNICH BO. MAUERKIRCHERSTR. 43

Dr. Itn KpUn ₀ . Darn. I MOncfc— «0, Moiwricifd)« r »trofl« 45 ·

ftr Zrtfc «.

ii

Ik fckralbM UmM 2 * fcw 22 84? EteSw «^ 5t 'SdP * 1972

Lawyer File # 22 84?

Matsushita Electric Industrial Co., Ltd.

Automatic frequency control circuit The present invention relates to an automatic ¥ re

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frequency control circuit, which will be referred to as AF control circuit in the following description, and both a television tuner or a television tuning device with variable capacitance diodes as voting agents, which are referred to as varactors in the following description is used.

Bfii an electronic voting device or at a Tuners that use varactors as tuning elements

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"C Π (St Κ 73) α Λ) Ο (" / Ο Ο) "S3 ΙΟ (" 33 10> TtUfrornnw: U (CSTA ^ fFATENT Mindvn TELEX OSUiM I6IG d Bonk, iay "risrfie Vereincbanl! MOndiei" töJ 100 fwhtW ;, MWorWn J5J 4J

is the feedback factor, i.e. the ratio of the Change in frequency of local oscillation to the AF control output frequency (MHz / V) is considerably larger than that of the usual inductive channel selector or the tuning device equipped with variable capacitors, so that the, difference between the holding ranges and the entrainment ocer capture ranges of the oscillator frequency becomes large, especially in the case of the UHF tuning device or the UHF tuner. Therefore, there arises a problem that a voltage to be applied to a varactor is not set can be. With the usual AF control devices therefore, the voltage that is maintained by the AF control generator and applied to the varactor is over Switching devices depending on the UHF and FM Dändem changed. Very specific switching devices must therefore be used; nevertheless the difficulty arises that the voltage that is applied to the varactor in one of the UHF and VHF tuning devices or tuners, becomes too small.

These difficulties can be overcome and eliminated by making the difference between the holding and Take-away or catch areas is made smaller.

The invention therefore provides a control circuit to the Difference between the stopping and take-away or catching areas to make it smaller. The object can be ao outgoing i L-det that the holding and Mitnahrae- or Fangbexeiche

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the VHF tuning device or the VHF tuner so narrow be made as possible Further is an AF controller created that is simple in structure and very reliable and safe in operation.

According to the invention, a DC tuning voltage is superimposed on an AF control voltage and applied to one side of a varactor in a UHF tuner or a UHF tuner (hereinafter referred to as UHF tuner), while the DC tuning voltage is applied to one side of a. Varactors in a VHF tuner or VHF tuning device (hereinafter referred to as VHF tuner) and the AF ^{1 control} voltage with a polarity opposite to the polarity of the AF control voltage applied to the UHF tuner to the other side of the varactor is created.

The invention is described below on the basis of preferred exemplary embodiments explained in more detail .. for which reference is made to the accompanying drawings.

Fig.l is a block diagram of a known automatic Frequency control circuit;

Fig. 2A is a diagram showing the relationship between the Frequency of the superimposition oscillation and the AF Re-

g is reproduced;

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FIG. 20 is a representation to explain the mode of operation the known AF control circuit in Fig.lt

3A and 3B representations to explain the unfounded Consequences if the difference is smelled by the stop

and the "" take-away areas are large}

Fig. K is a circuit diagram of the AF control circuit shown in Fig. 1 in the form of an IUackHchaltbilds)

Fig. 5 is a circuit diagram of an AF RegelungsBchaltung geinKN the invention ι

6 shows an illustration to explain the mode of operation of the

© r £ indungegcmKßcn circuit arrangement |

7 shows a circuit diagram of a first embodiment of an AF negotiation circuit according to the invention; and

FIG. 8 shows a circuit diagram in accordance with a wide design the invention.

Prior to the writing of the more detailed execution of the invention, the "well-known automatic" Froquonr-RegvlumcsschnltunjKt , Äi · In rims with AP> Kogelunc * (> chnl ~ beE "lchll (ti iit" Kur " ^ um Im «inr.eltini nuf-

there were no difficulties with the invention and b «)» | j, tlgi become · 1ηβ.

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The illustrated known, _n in Fig.l I form of a block diagram AF Rogelungßschaltuhg has an input terminal 1, a Mischotufe, 2, oinen Zwiachenfrequenz-Vorstarkor.3, a frequency-Dlskriminator 4 and a local oscillator. 5

• ι *

In Figure 2, the relationship between the AF-Uegolung voltage and the frequency of the superposition oscillation is shown; with the letter _{/ U} is a transmission constant (V / MHz) of the frequency discriminator and with the letter β a feedback factor (MHz / V). the frequency change of the superimposition oscillation with respect to the output of the frequency discriminator denotes, the slope or the steepness of the S-curve is .u, while that of the straight curve is 1 / ß.

In FIG. 2B, the mode of operation of the known AF-fiogelung shown in FIGS. 1 and 2A is operated. If a voltage applied to a varactor is changed in such a way that the frequency of the overlapping or unbalance of a frequency greater than the frequency f _Q. is, decreases towards the point D, then the frequency of the superimposed oscillation is taken by dio AF-nogelung in a range that is closer to the frequency f _Q. If the voltage impressed across the varactor is changed in the same direction, the frequency of the upper position oscillation is no longer regulated more easily by the AP control _S "and becomes equal to the rroquooa f _A. When the at dom varactor «dngoprügtu tension

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BATH ORIGINAL

in dor _e "it _{Rc ß} c" _{R. "ctaUll} Hichtung is changed, the frequency dor shall allow" _S oru is _ne, sh * i _"supply come in a range that _{nnhe the PreqUGna} ^ ^ _{the point B} i _ying . -lic AF _regulation is lost or stops at point O. The range of attic frequencies C _n and X _n is referred to as the entrainment or capture range, while the range between d, m frequencies f \ and f "al" is referred to as the stop range.

In FIGS. 3A and 3B, curves are shown to explain the unfavorable effects that occur when the difference between the entrainment or catching and the stopping areas is too great. The video carrier frequency plus the video intermediate frequency is f _y , while the audio _{carrier frequency plus the video intermediate frequency is f g} . If the voltage checked on the varactor is reduced so that the oscillator frequency is reduced from a frequency which is greater than the frequency f _g to a low frequency, then the oscillator frequency is _{carried along in the range of the frequency f s} , wia on location B is shown in FigOA. If the half-range extends to the point F and is wider than (fg + fy + drive range), then the oscillator frequency is not taken up to the frequency f _y , but jumps or jumps over to the frequency ff. This means that the voltage applied to the dom varactor cannot be adjusted. The Froquon »of the superimposed unsupported oscillation should, however, be up to the frequency f _y at the point H

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be taken in Fig.3A.

When the voltage applied to the varactor is increased so as shown in Fig.3D, then the oscillator frequency taken up to the frequency f .. at point I in Fig.3B · If the hold range is wider than the frequency difference (f_-f ..), and if the varactor angels ν

applied voltage is set to a value in the vicinity of the holding range I and is added to the varactor, if the channels change, the oscillator frequency is taken from the frequency f _e to the frequency f ...

• 9 Iv

To overcome these adverse effects described above and to eliminate must be the difference in holding. Reduced seam areas to> a minimum. Of the Feedback factor ß of the electronic tuning device or dos Tiuiers, in which a varactor * as an abstiraraelemont uses int, is considerably larger than the usual one AF control circuit in an inductive channel selector or a tuning device having variable capacitors. The difference uwisohen the Mltnahein and the Holding areas will be wider, as shown in Figure 2. This is particularly pronounced with a UHF tuner.

In Fig. K , the output voltage of an AF control voltage generator 6 is divided by means of resistors 7 and 8 and superimposed on the output voltage of a voltage jellyfish 9 for channel selection, which is applied to varactors 10 and 11, the

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is coupled to a tuned line 12 of a UHF oscillator circuit or to a tuned voice coil 13 of a UKl / oscillator oscillator. If the switch lk is closed while the switch 15 is open, you can receive on the UHF channel; but if the, channel Ik

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is open while the channel 15 is closed, can open on the VHF channel and the AF control voltage is divided by resistors 8 and 16. When the resistance 7 is greater than the resistor 16, then the

Feedback factor B when receiving on the UHF channel be the same as when receiving on the VHF channel; but the circuit shown in Figure 4 requires two switches 14 and 15; with her there is the difficulty that the Resistor l6 is too small to apply a sufficiently high voltage to the varautoradiodes.

In Figure 5 a circuit is shown which is not an embodiment of the present invention, but rather the principle on which the invention is based is advantageous is applied. The circuit shown in FIG. 5 has an AF control voltage generator 17 »a superimposed oscillator circuit 18, a Schmitt circuit 19, a switching transistor 20, which corresponds to the output signal the Schmitt circuit 19 is actuated ^ a switch 21 which is actuated in accordance with the switching of the transistor 20 is, a charging capacitor 22, a switch 23ι gcschlossen is when the capacitor 22 with that of einor

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Voltage source 2k supplied voltage is charged, a MOS transistor 25 for deriving the voltage at the capacitor 22 from the terminal 26, resistors 27 and 28, for superimposing the voltage at the terminal 26 of an AP Rege development voltage, a varactor 29 »a Resistor .28 for slowly discharging the capacitor 22 and a power source terminal 31.

In FIG. 6 the exact reception frequency is f_; the frequencies f. And f. "Are in the driving range between the frequencies f _p and f _Q ; the frequency f. ,, which is the oscillator frequency, if no AF control is taking place, is selected between the frequencies f. and f _A ". The voltage _{required for the frequency f A} is applied to the power source connection 31 or is applied to the terminal 26 of the MOS transistor 25 by closing the switch 23, so that the capacitor 22 is charged from the energy source 2k. The voltage at the energy source 22 is kept at a constant level by means of appropriate devices. For example, two local oscillators can be provided which oscillate to sweep the frequency corresponding to the breakover voltage and which are arranged so that when one oscillator starts sweeping, the other stops sweeping. The frequency width between the frequencies at the beginning and the end of the run is equal to the channel width; the alternating frequency sweeps by means of the two superimposition oscillators are

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Carrier frequency of the lowest TV channel started. the The number of alternating frequency sweeps is counted, and is swept at a predetermined number of frequencies the frequency sweep of a local oscillator is stopped so that the sweep voltage at which the frequency

sequence has been stopped, is used to adjust the voltage of the energy source 2k .

The capacitor 22 is gradually discharged, so that the voltage gradually increases to your terminal 26 · As a result, the frequency f in Fig.6., Slowly shifted to the right, so that the voltage E _n, gradually decreases to a value of E "at which voltage value the Schmitt circuit 19 is controlled or triggered. Thereby, the Schaltvaractor 29 is then actuated to close the switch 21, whereupon üer capacitor 22 begins to discharge through resistor 30th The tension on. the capacitor 22 is gradually lower, so that the frequency f., gradually decreases up to the frequency f.

In general, the Schmitt circuit has a hysteresis such that the frequency f. ,, if between the frequencies f. and f "lies between the frequencies f ^ and f." swings. As a result, the reception can be halfway reduced by means of the circuit shown in FIG be performed. The difference between the frequencies f. and f. ,, but must be chosen so * that the frequency

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f ,, is dax-daxed as in Fig. 6, '"lies between them; but if the AF control voltage for UHF and FM reception, as shown in Figure 5; is the same, then the difference between the frequencies f. and f. ,, at FM reception extremely poor. This difficulty can be overcome and eliminated by eliminating the feedback factors can be made the same when receiving on both the UHF and VHF channels. The present invention is based on this fact and is described in detail below with reference to preferred exemplary embodiments.

The in / Fig. illustrated automatic frequency control circuit according to the invention comprises a varactor 32 in a UHF oscillator-resonant circuit, a varactor 33 in a VHF tuned circuit, a tuned cable Jk in the UHF oscillator resonant circuit, a tuned Scliwingspule 35 i ⁿ the FM oscillator resonant circuit, and an AF control voltage generator jG in, for example, an integrated circuit, the output circuit of which is a differential amplifier; Furthermore, the automatic frequency control circuit has resistors 37 and 38. for dividing the AF control system when receiving on the UHF channel, an energy source 39 for applying the voltage required for channel selection to the variable capacitance diode ^ fO. a. Output connection for the AF control system, for the "UIlF channel selection, an output connection for the AF control system, ... _v

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voltage for the VHF channel selection, resistors 42 and kj for sharing, the AF control voltage when received on the VHF channel, a capacitor 44 for grounding the connection between the varactor 33 ^UIJLt * of the tuned transducers! c 35 »a ^ energy source 45 for the VHF local oscillator and an energy source 46 for the UHF local oscillator.

The frequency change speed corresponding to a voltage applied to a varactor used as a spacer element is applied is considerably larger than the frequency change corresponding to the voltage

/ in '' ■■ '■■ ^: · "■■ ■■■"'

"which to a variable, an AF control with-.

by means of an inductive channel selector or one with changeable Capacitors equipped tuning device used capacitor is applied. The rate of change of frequency is considerably larger when received on the UHF channel than when received on the VHF channel «As a result can the ratio between the resistors 3? and 38 can be made so large that the voltage drop across the Energy source 39 is negligible; the ratio between the resistors 42 and 43, however, which is used to divide the AF regular voltage are used in corresponding values, can be made as high as the ratio between resistors 37 and 38. The AF * Regolungfispaimimg with opposite Polarities are at the terminals 40 and

•. ■ ■ ■ ■ ■. ■ '.. / ■, 4l obtained; the polarities of the vnractors on which the

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AF control voltages are applied must be reversed. For this purpose, the capacitor kk is connected between the connection of the tuned contact coil 35 and the resistor 53 as well as earth «

. is ii 'The second embodiment of the invention illustrated in Figure 8 is substantially the shown in Figure 7 is similar except that the cathode of the varactor 33 is connected directly to the connection between the resistors 37 and 3, respectively. The ratio between the resistances 37 and 38 is considerably greater than the ratio between the resistances k2 and 43; the AF control voltages obtained and divided at the connections kO and kl are applied to the varactor 33. As a result, the second embodiment has only one input terminal ^ 9, while the embodiment shown in Figure 7 has two input terminals 47 and kS for the tuning voltages be.

In FIGS. 7 and 8 there are also resistors 51, 52 and 53 and a voltage source 50 for forming an AF control bias provided on the VHF tuner when one end of the tuned line 35 in the VHF tuner is grounded and the voltage top pulse frequency set in your FM tuner is that the synchronization between a high-frequency amplifier tuning and the local oscillator oscillating circuit can be reached.

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In the first embodiment shown in FIG. 7, the tuning voltage superimposed on the AF control voltage is applied to one end of the varactor in the UHF tuner, while the tuning voltage is applied to the other end of the varactor in the VHF tuner and the AF control voltage is applied to it other end is applied, so that the ratio between the resistors 37 and 38 across which the tuning voltage is applied from the power source 39, accordingly

~ can be made larger. The ratio between the resistors 42 and kj for dividing the AF control voltage applied to the VHF tuner can be set independently of the ratio between the resistors 37 and 38, so that the difference between the frequencies f and £ *. as described in connection with Figures 5 and 6, can be considerably larger; ie. the feedback *; - factor ß can be reduced to a required value.

It should be noted that the aforementioned functions can be achieved without any switching device. Furthermore, it is not as simple as in the case of the coil 35 in the VHF tuner that the ground connection of the tuned line "} k in the UHF tuner is floating dc, but is grounded with respect to the high frequency, so that the circuit -complicated and the efficiency is worsened. The matched line 3 * t in Pig.7 and 8 can be a line matched to 'i / k or Λ / Ζ

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Claims (3)

According to the invention it is advantageous to apply the tuning voltage to one terminal of the varactor and the AF control voltage to its other terminal. In the second exemplary embodiment shown in FIG. 8, the AF control voltage for the UHF tuner is divided, the tuning voltage in the VHF tuner is superimposed and applied to the varactor 33 i * 1 of the VHF tuner, as the ratio between the resistances 37 and 38 is sufficiently large so that the AF control voltage for the UHF tuner is equal to the * AF control voltage for the VHF tuner, which is obtained at the terminal kl and divided by means of the resistors 13 and 13 While in the first embodiment shown in FIG. 7 input connections for the tuning voltage for the VHF and UHF tuners must be provided, in the second embodiment shown in FIG Tuning voltage can be used so that the circuit is simpler in structure and less complex to implement 1. / Automatic frequency control circuit g e k e η ri draws by (a) a UHF tuner with a varactor (32) as a detachment element, (b) an FM tuner with a varactor (33) as a tuning element, . - (c). a generator (36) for generating automatically frequency-regulated Voltages of opposite polarity; (d) a DC voltage source (39) for applying a channel -I optional voltage to the varactors (32 »33) as well as in the UHF as well as in the FM tuner; (e) Means for superimposing the tuning voltage of one of the automatically frequency-controlled voltages and for application to one end of the varactor (32) in the UHF tuner; and - (f) Means for applying the other automatically frequency-controlled Voltage at the one end of the varactor (33) in the VHF tuner and for applying the tuning voltage on the other side. 2. Automatic frequency control circuit still claim 1, marked by the fact that the AbHiäinimspan'-nung only on one side of the varactor (33) - in the FM tuner is created. - 17 - 3098U / 0P50 3. Automatic Fr-equen.ssr-egeluiagsschaltun.g according to claim 1, characterized in that on one side of the varactor (33) in the VHF tuner applied the tuning voltage is that of the automatically frequency-controlled voltage of the generator (36) is superimposed « k. Automatic frequency control circuit according to Claim 2, characterized in that the output connection of the direct voltage source is coupled to one side of the varactor (33) in the VHF tuner, and that the output connection of the one automatically frequency-controlled voltage of the generator (36) is coupled to one end of the varactor ;. (32) is applied in the UHF tuner via a series connection of two resistors (37, 51), and that the connection (49) is coupled between the series-connected resistors (371 51) via a resistor (48) to the output terminal of the DC voltage source (39). 5 · Automatic frequency control circuit according to claim 3i characterized in that the output terminal one automatically frequency-controlled voltage of the generator (36) on one side of the varactor (32) in the XfHF tuner via a series connection of two resistors (37 * 51) is coupled, uiid that the connection between the two resistors connected in series (37 »51) about a. Resistance (38) to the output terminal of the DC voltage source (39) and via a resistor (52) - 18 - 30 98U / 08SQ \ to the other end of the varactor (33) in the FM tuner is coupled. 3098U / 0880